Kind of looking back at Blizzard's formula for how they have built up villains. A theme that occurs often is when a big bad guy is designated in the beginning, and as the story progresses we see he/she/it is struggling with some inner turmoil in regards to loyalties or moral, and then at the climax he/she/it ends up turning good OR doing that one sacrificial good deed to help the protagonists.
The 7.2. trailer certainly implied frustration Kil'jaeden has with Sargeras due to (in his mind) the consistent failures of the Burning Legion. Frustrated enough to make it to the level of almost BLAMING Sargeras.
And also, unless I'm looking too much into it, you can tell during the scene of Kil'jaeden watching the dudes @ Krasus Landing speak that when Velen begins talking about the true masters of the Legion revealing themselves, and speaks about Kil'jaeden (calling him a monster, etc)... the look of utter sadness on KJ's face followed by anger. He looks almost... hurt still.
Perhaps this is more of a rant, or a maybe a plea, but please do NOT have KJ ending up turning on Sargeras to the benefit of us.
Mannoroth and Archimonde were evil and against us to the end.
KJ is supposed to be infinitely more evil and devious than they.